Prelude: Ensuring Inter-Domain Loop-Freedom in~SDN-Enabled Networks

TL;DR

Prelude introduces a privacy-preserving system using Secure Multi-Party Computation to accurately detect inter-domain forwarding loops caused by SDN policies in SDXes, enhancing correctness and privacy in inter-domain routing.

Contribution

The paper presents a novel SMPC-based primitive and a distributed system for detecting SDN-induced forwarding loops without revealing private routing information.

Findings

100x fewer false positives compared to previous solutions

Improved privacy guarantees in loop detection

Enhanced efficiency leveraging SDX-specific properties

Abstract

Software-Defined-eXchanges (SDXes) promise to tackle the timely quest of bringing improving the inter-domain routing ecosystem through SDN deployment. Yet, the naive deployment of SDN on the Internet raises concerns about the correctness of the inter-domain data-plane. By allowing operators to deflect traffic from the default BGP route, SDN policies are susceptible of creating permanent forwarding loops invisible to the control-plane. In this paper, we propose a system, called Prelude, for detecting SDN-induced forwarding loops between SDXes with high accuracy without leaking the private routing information of network operators. To achieve this, we leverage Secure Multi-Party Computation (SMPC) techniques to build a novel and general privacy-preserving primitive that detects whether any subset of SDN rules might affect the same portion of traffic without learning anything about those rules. We then leverage that primitive as the main building block of a distributed system tailored to detect forwarding loops among any set of SDXes. We leverage the particular nature of SDXes to further improve the efficiency of our SMPC solution. The number of valid SDN rules, i.e., not creating loops, rejected by our solution is 100x lower than previous privacy-preserving solutions, and also provides better privacy guarantees. Furthermore, our solution naturally provides network operators with some hindsight on the cost of the deflected paths.